Insertional Mutation

The insertion of a transposable genetic element within a gene disrupts its function and as a consequence, leads to lethal effects or altered functions (see Fig. I36). The insertion may modify the expression of the target genes by overexpression, suppression of the mutant phenotype or alter it. It has been recently demonstrated that many of the insertions do not lead to an observable change in the expression of the genes or their effect is minimal and only sequencing of the target loci reveals their presence. Labeled probes for the insert can selectively isolate the gene carrying the insertion. Although it was initially believed that the insertions occur at random sites, it has now been documented that the target sites upstream of the promoters or other locations where no essential functions are disrupted are preferred.

Figure I36.

Insertional mutation of Arabidopsis knocked out the stem but fertility of the fruits is retained. (Rédei, unpublished)